SPRING HONEY: NEW MYSTERES OF SMELL CODE

       

A formist mechanism for activating of olfactory receptors by odorant molecules is commonly accepted by the scientific community. It is based on an interaction of the enzyme-substrate type.

Vibrational theory proposed by biophysicist Luca Turin in 1996 indicates that the olfactory receptors selectively capture the vibrational energy of odorant molecules. Since then there is much controversy on this subject, without definitively has definitively closed the debate.

Recently, in February 2016, a group of Italian scientists from the University of Trento, led by Marco Paoli have published an interesting work that brings new light to that discussion. They have found in bees isotopic isomers of odorant molecules activate different olfactory glomeruli of their non-deuterated counterparts. (Two isotopic isomers differ only in their hydrogen atoms have been replaced by deuterium atoms, hydrogen atom identical, but with double mass.)

They have also verified that all bees’ glomeruli are sensitive to isotopic detection of odorants and only some of them are particularly sensitive to such detection. The aforementioned detection mechanism is not a substitute for formist one, but could be a variant or simply a complement of it.

 When it comes to very similar molecules, such as isotopic isomers or isotopomers, comes in a new way to detect odours. The conclusion of this work allows to authors of the same insinuating that it is possible that the mechanism by which bees capture odorant molecules is the vibrational type. Some recent work by other authors suggests the possibility of differentiating processes of isotopic odorant molecules in humans.

At this point, we ask the following: In our atmosphere there deuterated odorants in abundance?

The answer is no. So what biological sense has such kind of discovery?

To answer that second question we consider the following hypothesis: "The mechanism of differentiation between odorant molecules deuterated is an obsolete and non functional mechanism. This would mean that the said mechanism generated by evolution, was operating in past times. It has now been deprecated, but is still there, in the genotype of some living things. "

Note that, although certain isotopes, under laboratory conditions, activated glomeruli bees of antennal lobe, does not mean that they in their daily life, they go through the countryside smelling such isotopes. Nor do we know what happens when activated in vitro such glomeruli: Bees smell something? If the mechanism is really obsolete, most likely not experience any olfactory sensation.

 Then a new question arises: When did that ability to differentiate isotopes in bees?

We propose a new hypothesis: "Possibly emerged in the process of evolution of the first insects, more than 300 million years ago in the so-called Devonian period. In those days it was quite possibly the most abundant deuterium now in the Earth's atmosphere and not be surprising that certain flowers synthetized odorant molecules, such as rose, carnation and jasmine incorporating deuterium sap. The evolution allowed discrimination of her homologues not deuterated. Bees, hundreds of millions of years later, inherit the first insects that special sense of smell. "

Following the above, the question of whether the ability of bees to distinguish odorants isotopes due to the vibrational theory of Luca Turin is still in the air. We believe that new laboratory tests should be carried out, for example verifying the role of NADH or Zn ⁺² to answer yes or no to that question.

 In any case it seems that the early bees of Cretaceous preferred make their honey with flowers less contaminated with heavy elements, such as hydrogen isotope still young. The evolution allowed choosing what suited them. Possibly the honey of spring, tasty and nutritious, was more digestible for the larvae of bees from plants that that with deuterium in his veins.

Below we briefly summarize the basics of conformist and vibrational theories. Also we recommend two bibliographic items for anyone who wishes to go deeper into the subject.

The formist recognition model of odorant molecules by the olfactory system is based on certain properties of this class of molecules, such as size, shape, electric charge and hydrophobicity of them. It is a key-lock type model in which the odorant molecule (ligand) interacts with the olfactory receptor, a protein-membrane 7, anchored in the cell wall of the olfactory neuron.

The process involves activating olfactory receptor by a conformational change of the protein structure forming the olfactory receptor. This activation triggers a cascade of enzymatic reactions and the formation of an electrical pulse which is transmitted by the neuronal axon to a glomerulus, or place of concentration of neural impulses in the olfactory bulb.

The olfactory bulb is a brain area in which the glomeruli are stored, something like the dresser of different types of aromas and perfumes that we perceive.

The interaction of neurons in the olfactory bulb with others from different parts of the brain is different maps of olfactory sensations. When we notice a smell is illuminated one of those maps, consisting of hundreds of thousands of synaptic connections between neurons. Actually odorant molecules are odorless and only serve as a key that activates the olfactory sensations, a paradox. We smell to the brain.

In humans there are 347 functional olfactory receptors and about 650 are inoperative. This is because in the family of genes encoding proteins most thereof are pseudogenes, or genes that have lost their functionality, possibly along evolution. This family of genes, that encode olfactory receptors, was discovered in 1991 by Americans Richard Axel and Linda Buck. For this work received the 2004 Nobel Prize in medicine and physiology. Later they work also showed both how smell works following a rules similar to the unlimited capacity of combination of the digits of a padlock.

In the vibrational theory proposed by Luca Turin, nose acts as a biological spectroscope. Odorant molecules vibrate due to its atomic bonds. When excited with the energy of coenzyme NADH, a specific amount of energy released, it is selectively taken up by the olfactory receptors, thanks to a complex quantum inelastic tunneling mechanism.

Bibliography:

- Bridging the Olfactory Code. Francesc Montejo. Perfumer and Flavorist. July 2009 Vol.37, No. 7.

- Odour Differential Coding of Isopomers in the Honeybee Brain. Marco Paoli et al. Scientifics reports. University of Trento. February 2016.